Roofing structures can be constructed using a number of different methods and roofing systems. One common system, commonly used for retrofit roofs, is the post and purlin system. The post and purlin system includes a plurality of elongated vertical support posts fastened to the existing roof substrate. A network of base beams fastened atop and flush to the existing roof substrate may be used to strengthen the web of posts. The vertical posts may be fastened directly to the roof substrate or to the base beams fastened to the substrate.
Fastened to an upper end of the vertical posts are horizontal purlins that run perpendicular to the vertical posts in the horizontal plane. The height of the horizontal plane varies at each intersection based upon the pitch or slope of the roof. For example, a horizontal purlin may intersect with a vertical post at 10′ relative to the roof substrate at the eave of the roof, and at 16′ at the ridge. Posts and purlins may be found at locations intermediate the eaves and ridge of the roof Importantly, the post length and positioning of the purlins about the posts must be consistent with the desired pitch of the roof.
Zee-shaped purlins (“zee purlins”) are commonly used in roofing systems. These purlins get their name from their similarity in shape to the letter Z. Zee purlins are comprised of three faces, a top face (generally horizontal), a vertical face, and a bottom face (generally horizontal), shaped to form a generally Z-shaped device. A straight zee purlin is one with the faces meeting at roughly 90°.
Mounted atop the purlins may be any variety of roofing panels with or without intermediate insulating material. The roofing panels are designed to mount relatively flush to the top faces of the network of horizontal purlins.
Brackets are used for fastening the vertical posts to the purlins and brackets may be used for fastening the vertical posts to the roof substrate. Workers place brackets in desired positions and drive fasteners through a bracket and into the vertical posts, the vertical faces of the purlins, or the roof substrate.
In some instances, the desired pitch is accounted for in the shape of the horizontal purlin. Here a straight zee purlin may be bent such that the top face meets the vertical face at an angle other than 90°, in order to account for the pitch of the roof The vertical face would mount flush with a bracket at a generally vertical orientation. This approach obviates the requirement to rotate the bracket to the desired pitch (to be discussed shortly), but does require custom fabrication of the zee purlins. This process is cumbersome and expensive, as special equipment located off the job site is often necessary to fabricate the purlins to the desired angle.
In other instances, a straight zee purlin is used and the bracket is rotated to pitch prior to fastening to the vertical post. This is considered the more conventional approach in the art and is illustrated in U.S. Pat. Nos. 6,240,682 and 6,470,644 (hereinafter collectively referred to as “James et al.”).
Rotating and fastening the bracket to the post and purlin is considered one of the more challenging and time consuming aspects to such an installation. This requires the installer to measure the roof slope using an angle finder or similar device, rotating the roofing bracket to accommodate the slope, and fastening the bracket to the vertical post at the appropriate angle.
It is desirable in the art to make the installation of a roofing system more efficient without compromising the safety of the installers or the structural integrity of the roofing system.